i have on 02 plate wrx with about 290bhp

and it started to missfire under hard acceleration at about 5k but it is fine if you accelerate slow it will go to the limiter if you floor it its as if the limiter is at 5k

so i canged the maf sensor then the plugs then the coil packs so im about £600 out of pocket and the problem is still thier any help would be much apreciated thanks mike

 

Could be plug leads.
Check you used the correct plugs with a .7mm gap or less.

 

ye they were the same plugs that i took i out i will check the gap tho

any other ideas

 

Plug leads cause exactly what you describe. No problem on light medium throttle but miss fire on hard boost.
If you are replacing, stick with O/E Subaru. Some dealers will give you a good discount on them, if not, try Roger Clark Motorsport.
Last set I got, all be it for a M/Y 98 were under £50.

 

it does not have leads on this mod mate it has 4 coil packs and iv changed them

thats why i am so confused coz its normally that

i think it could me the fuleing of it may be over boosting

 

Sorry, should have said coil packs. Around £50 each.
If you are getting a fuel related missfire at high boost because it is weak, that is very worrying because you will melt a piston etc.
This is very easy to check.
Where are you located???
You need someone to check your AFR with a wideband. If you were near here I would simply put an LM1 on it with a probe up the back box and look at the AFRs, warmed up foot flat on the floor. This needs immediate attention and hopefully elimination.
What ECU do you have???

 

i am puting it into dp motorsport on wed mate and i will drive it off boost all the way thier

i am located in liverpool

i think it could just be the fule pump im not sure tho it has be baffled now

and my ecu is just standared with a remap from powertune

thanks for your help mate

 

When the re-map was done was a uprated fuel pump fitted. If not you could be beyond the fuelling limit of the OE pump. Which would cause the fuelling to be lean as the pressure will be insufficient. Hope you get it sorted fast m8

 

no it is a standared fule pump that what im hoping it is now thanks for the help mike

 

i had similar probs in a uk99 turned out to be a leaking exhaust manifold to up pipe gasket. and the up pipe was split. leaking exhaust gases
and i had a broken/split ceramic on one of the spark plugs as well